For centuries, it was known that people who survived smallpox became immune to it. For that reason, nearly every culture tried to induce immunity in healthy individuals. The Chinese used tubes to insert powdered smallpox scabs into their nostrils. In Turkey, pus from lesions was scratched into the skin.
Climate graph San Francisco. The driest month is July. There is 1 mm of precipitation in July. Most precipitation falls in January, with an average of 115 mm. Temperature graph San Francisco. With an average of 17.6 Â°C, September is the warmest month. In January, the average temperature is 10.4 Â°C. It is the lowest average temperature of the whole year. San Francisco Climate table // historical Weather data
Averages for San Francisco in May. May is one of the best times to visit the city, in terms of the weather, with clear blue skies and little fog expected.When packing, take light, summery clothes that you can wear in layers, with a warmer jacket.here are 11 hours of sunshine expected per day throughout the month. Be sure to pack a waterproof jacket, though, as there is an average of 18 mm of rain anticipated over 4 days throughout the month. If you enjoy going in the sea, the average temperature throughout May will be 12 C.